I'm in the first year of Biology, and I don't have that much experience or background knowledge about the subject. I'm doing an experiment about yeast fermentation on different kinds of sugars, but i'm having more trouble with this than I thought I would...

1.) I read that sucrose, glucose, and fructose can be fermented while maltose, sorbose, and galactose cannot. Is there an explanation why?
2.) I'm having trouble finding the difference between fructose and glucose.
3.) Would artificial sweeteners ferment?
4.) Where can I find sugar? I know that sucrose is table sugar and fructose can be found in corn syrup... but other than that, would I be able to base my conclusions on sugars found in things bought at the store, or would there be too many different factors affecting the outcome? Do I need to test PURE sugar?
5.) Are there any ways that I can measure fermentation? I've read about pressure gauges and upside down tubes etc to measure CO2, but are there any other ways?

1) The ability to utilize a sugar other than glucose depends if an organism can degrade ( if the sugar is polysaccharide ) or convert (if the sugar is monosaccharide ) it to glucose/fructose. For example, galactose can be converted to Glc6P by yeast, so i think your source is not very correct ( although indeed galactose is not as good as glucose, because it requires conversion ). You can check for sugars which can be fermented by eukaryotes right here:
http://www.biocarta.com/pathfiles/feederPathway.asp(Note: different kinds of prokaryotes know to ferment anything you can imagine! )

3) If you mean those that are used by diabetics then they will not be. It's all the sense of artificial sweeteners that they can only act on taste receptors giving you sweet taste but not raising glucose level in blood. Just check for structure of famous saccharine that is not a sugar at all:
http://en.wikipedia.org/wiki/Saccharine

4) Pure sugar is the best. If bought sugar suddenly contains arsenic or mercury compounds all results will
get screwed.

5) Just drink the fermentation products. Compare the effects with the same dose of vodka ( vodka 40% of ethanol ). The stronger the effects the better fermentation ( more ethanol was produced ).

Hi, I make wines, beers and cordials for my friends and family and know a bit about the subject. Alcohol is produced by yeasts fermenting sugars that are fermentable. (Actually there are chemicals that will ferment lactose and those are found a problem in lactose-intolerance but I digress.) Fructose, sucrose, glucose, maltose and a few other sugars are fermentable by commercial yeasts. Maltose makes excellent beer by the way.

The vodka experiment is interesting but it cheats in the sense that vodka is produced by a fermentation process that is furthered by a distillation process. In nature, most yeasts top out at an alcohol concentration of between 12-20% by volume. It takes a "super yeast" to get a 20% value. I know because I do that for cordials.

Alcohol kills yeasts when it reaches a certain concentration. Basically, alcohol is an excretion product of yeasts and just as with humans, there is only so much "waste product" a yeast can handle.

sorrels wrote:The vodka experiment is interesting but it cheats in the sense that vodka is produced by a fermentation process that is furthered by a distillation process.

No cheating. Here vodka is mentioned not as an example of fermentation end-product but only as a measurement of alcohol concentration. Of course one can choose to use arak as a reference frame instead of vodka but it will be a little more problematic ( http://en.wikipedia.org/wiki/Arak_%28Di ... everage%29 )

Dear druid, Your posting gave the impression that vodka was produced by fermentation directly. That was the nature of my disagreement.

I will quote: "Just drink the fermentation products. Compare the effects of vodka (vodka 40% of ethanol). The stronger the effects the better fermentation (more ethanol was produced). Your comment does not even allude to distillation but offers the impression that vodka is produced by fermentation. Please be careful when you try to misquote me.

Hi, i am doing one project in which my teacher wanted me to get 0.5 L of vodka.
I tried several experiments with several values, even values which close to theoretical formula of ethanol fementation. But at the end of this experiments i just got veyr low results. i use melase as sugar source. i need help for better results...if u answer me i will be very glad.thank you very much

i made fermentation. And then i want to distilate it in order to get mixture of only water and ethanol. But there is smell if u dont make filtration, and if u make u lose ethanol. Can u suggest me what to do?